The present invention relates generally to bearing systems for relatively rotatable conduits conducting a liquid, and more particularly to such a bearing system including a protective casing surrounding operative parts of the system to minimize entry of external dirt and other abrasive material, the casing including means permitting bleeding therefrom of leakage liquid which collects in the casing during use.
The invention finds particularly advantageous application with rotatable sprinklers widely used for irrigation purposes, and a preferred embodiment of the invention will be described in connection with such an application. However, it will be seen that the invention is not limited to such an environment, but can find application in other environments as well, where two relatively rotatable liquid-carrying conduits are connected together in an environment having dirt, dust and other abrasive material whose entry would be harmful to the operative parts of the bearing system.
A typical bearing construction of the type under discussion consists of a bearing housing having a cylindrical bore therethrough and an external upwardly directed annular shoulder. Rotatably mounted within the housing bore is a tubular spindle having a lower annular flange, the spindle upper end projecting above the bearing housing and being connected to an outlet member such as a sprinkler head. The outlet member is provided with an annular downwardly directed shoulder in coaxial alignment with the shoulder of the bearing housing. Annular seals are provided, including lower seal means between the spindle flange and the lower end of the bearing housing, and upper seal means abutting the annular shoulder of the outlet member.
Resilient means are provided for maintaining the upper and lower seal means under a predetermined amount of compression, typically including a helical spring which bears at its lower end against the upwardly directed annular shoulder of the bearing housing, and at its upper end against the annular seal means contacting the downwardly directed shoulder of the outlet member. It is found that external mud and dirt become encrusted on the helical spring, and abrasive particles of such dirt and mud can pass into the small annular clearance between the rotatable spindle and the fixed bore of the bearing, scoring and galling those otherwise smooth surfaces, and eventually binding the spindle against rotation.
In order to minimize entry of abrasive particles of mud, dirt and dust into the operative parts of the bearing system, it has been previously proposed to provide an annular cover in the form of an integral corrugated bellows of suitable material such as plastic, surrounding the spring. However, difficulties arise in the use of such a bellows because the internal seals of the bearing system inevitably leak, and pressurized liquid from the supply conduit collects within the annular chamber formed by the bellows. The force of this pressurized liquid effectively adds to the force of the spring itself, imposing much more thrust load on the rotating parts, particularly the upper seal, than was intended in design, eventually leading to binding of the parts. The strength of the spring is so chosen as to impose a predetermined optimum force on the relatively rotable seal components. Hence the spring should be unrestricted in its free longitudinal expansion to maintain that force despite manufacturing tolerances, and to gradually continue that expansion as the seals wear over their useful life.
In accordance with the present invention, there is provided an annular casing assembly surrounding the helical spring of the bearing system and forming effectively the outer wall of a chamber within which the spring is disposed. The casing assembly includes a lower annular case of suitable rigid material such as metal or a rigid plastic, having a smooth cylindrical outer wall and an inwardly extending lower flange underlying the helical spring. The casing assembly includes also an upper annular cap having an internal flange overlying the upper end of the helical spring, and a downwardly depending generally cylindrical sidewall spaced slightly outwardly from the outer sidewall of the annular case, the depending sidewall of the cap being provided at its lower end with an inturned feathered edge which lightly contacts the outer cylindrical sidewall of the case. The material of which the sidewall and feathered edge of the cap are formed is resilient and flexible, so that even a very slight liquid pressure within the annular space between the sidewalls of the cap and case will cause the feathered edge to move slightly outwardly away from direct contact with the case cylindrical sidewall. The small opening thus provided permits liquid collected in the chamber to bleed outwardly and downwardly, thereby preventing the building up of liquid pressure within the annular chamber formed by the casing assembly. When no liquid is in the annular chamber, the feathered edge of the cap remains in contact with the case sidewall, thus preventing entry of external abrasive material. In order to facilitate the opening movement of the feathered edge away from the case sidewall during bleeding, it may be desirable to provide one or more vertical slits in the lower portion of the sidewall of the cap, extending upwardly a short distance from the feathered edge.
It will accordingly be seen that the casing assembly, and more particularly the contact between the lowermost feathered edge of the cap and the cylindrical sidewall of the case, constitute in effect a check valve permitting outward and downward flow of liquid, but preventing flow of any material in the opposite direction.
It is accordingly a principal object of the present invention to disclose and provide a novel protective casing assembly for a bearing system connecting two relatively rotatable liquid conducting conduits. Other and additional objects and purposes are to provide a novel two-piece casing assembly for forming, with a bearing housing, an annular chamber for housing a helical spring; to provide such a casing assembly including check valve means for permitting bleeding exit of leakage water from the chamber, while barring entry of external abrasive material; to provide such a bleeding protective means which facilitates assembly during manufacture; and for other and additional purposes as will become clear from a reading of the following description of a preferred embodiment of the invention, taken in connection with the accompanying drawings.